Pollen immunotherapy: selection,prevention, and future directions.

Pollens are an important cause of allergic rhinitis and asthma. Pollen immunotherapy is effective and potentially curative. It has been shown to prevent new sensitizations, to prevent the development of asthma in children, and to induce long-term benefit. Standardization of allergen extracts is necessary to improve immunotherapy safety and efficacy. Knowledge of the local plant taxonomy and allergen cross-reactivity is important in selecting clinically relevant vaccines. In general, allergenic cross-reactivities correspond to taxonomic relations. Tree and weed species demonstrate variable degrees of cross-reactivity. Most grasses have extensive allergenic cross-reactivity. Mechanism of action continues to be an area of investigation, including the induction of immunoglobulin G blocking antibodies. Sublingual immunotherapy, concurrent anti-immunoglobulin E use, hypoallergic peptides, and DNA vaccines are other promising technologies.